fixup! Add the outline for structured output

Author: KrishanBhasin

src/pip/_internal/commands/index.py

@@ -147,7 +147,7 @@ def get_available_package_versions(self, options: Values, args: List[Any]) -> No
                 }
 
             if dist is not None:
-                structured_output["installed_version"] = dist.version
+                structured_output["installed_version"] = str(dist.version)
 
 
             write_output(json.dumps(structured_output))

tests/functional/test_index.py

@@ -29,7 +29,7 @@ def test_json_structured_output(script: PipTestEnvironment) -> None:
         "1.5.2, 1.5.1, 1.5, 1.4.1, 1.4, 1.3.1, 1.3, 1.2.1, 1.2, 1.1, 1.0.2,"
         " 1.0.1, 1.0, 0.8.3, 0.8.2, 0.8.1, 0.8, 0.7.2, 0.7.1, 0.7, 0.6.3, "
         "0.6.2, 0.6.1, 0.6, 0.5.1, 0.5, 0.4, 0.3.1, "
-        "0.3, 0.2.1, 0.2" in structured_output.get("versions")
+        "0.3, 0.2.1, 0.2" in ", ".join(structured_output.get("versions"))
     )
 
 @pytest.mark.network